I have a 40 GB USB hard drive formatted with NTFS on a PC running Windows XP Pro, SP3. I am trying to free as much space as possible. Windows Explorer tells me that I have about 200 MB of files on the drive (showing hidden and system files). When I show drive properties however it shows 73% free, around 10 GB used.

I ran CHKDSK and it found all kinds of problems.

Now running defrag and it is behaving as if there were 10 GB of files, but I can't access them anywhere.

that is a good point, cleaning out old system restore files can be a HUGE help in this area.
–
Happy HamsterMay 18 '09 at 5:30

Great suggestion -- ran Sequoia View as SYSTEM and it immediately showed me that I had about 3.7 GB of restore files. Disk cleanup was not able to remove them (why do I have restore files saved on my removable USB drive anyways??). Now trying to figure out how to delete as SYSTEM...
–
jacobseeMay 26 '09 at 14:44

I'll probably end up reformatting as per your other suggestions rather than mess with this any further...
–
jacobseeMay 26 '09 at 14:46

1

Disabled system restore for this drive only and that reduced the reported used size a bit. Then used psexec -s cmd to get a system shell and deleted the restore files. I'm down to 1.6 GB used. Disk defrag / analyze / view report tells me the MFT is 1.45 GB, so I'm going to try your other suggestion of just reformatting to clear that.
–
jacobseeMay 26 '09 at 15:17

after formatting and copying back the files, MFT is down to 160 KB, quite an improvement!
–
jacobseeMay 26 '09 at 16:40

Alternate data streams allows files to be associated with more than one data stream. For example, a file such as text.txt can have an ADS with the name of text.txt:secret (of form filename:streamname) that can only be accessed by knowing the ADS name or by specialized directory browsing programs. Alternate streams are not detectable in the original file's size...

1) I have often seen on client (and my own) computers that when free space gets very low (less than 1%) when files are deleted, they do not free up the appropriate amount of space (delete a 1 gig file, only get 500 MB back).

2) I have never found a way to recover ALL of this space, but I have found a way to recover some, which I will outline below:

Steps to clear out the page file area -

1) Right click on "My Computer" and select properties

2) Click the advanced tab

3) click "settings" under "performance"

4) Click the advanced tab again

5) Under virtual memory, click "change"

6) Set the page file to 0 MB, then "okay" out of all the screens and restart the computere